Previous exposure to SARS-CoV-1 or HCoV-OC43 may provide some cross-immunity against SARS-CoV-2.

“Previous studies have found that SARS-CoV-1 can generate neutralizing antibodies against HCoV-OC43 which could offer cross immunity and HCoV-OC43 can generate cross-reactive antibodies against SARS-CoV-1. Additionally antibodies from sera, from people with HCoV-OC43 coronavirus responsible for the common cold or found to cross react with SARS-CoV-2 antibodies. It was also found that people infected with SARS-CoV-2 also increase their preexisting antibodies against the classic cold coronavirus. Antibodies produced in response to infection from SARS-CoV-1 cross-react with SARS-CoV-2 because the spike proteins for both viruses are similar enough to each other.”